The evergreen perennial ferns Dicranopteris linearis and Gleichenia japonica (Gleicheniaceae) form dominant communities on various types of naturally and artificially disturbed sites. In the present study, we examined the effects of leachate from various organs of the ferns (donor plants) on the germination and growth of lettuce (receptor plants) under laboratory conditions to test the allelopathic potential of the extracts. Several types of leachate from donor materials (including fresh and senescent leaf lobes) significantly inhibited the radicle and hypocotyl growth of lettuce. No donor materials promoted lettuce growth. Because solution and experimental conditions such as pH, electric conductivity, and incubation temperature were adequate to ensure lettuce growth, it is reasonable to conclude that the observed inhibition of lettuce growth was mainly caused by allelopathic chemicals leaching from the ferns. Reduced lettuce growth suggests the possibility that D. linearis and G. japonica dominance in the field results partly from their allelopathic activities.

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